This invention pertains to the valve art, and, more particularly, ball valves. The invention is particularly applicable to a new and improved ball valve incorporating a low dead space ring and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and could be adapted to use in other types and styles of valves.
Commonly assigned U.S. Pat. Nos. 3,894,718 and 4,410,165 detail the evolution and development of seal assemblies utilized in ball valves, the disclosures of which are hereby incorporated by reference. Generally, early developments of valve seat assemblies for ball valves employed an elementary seat design which included a pair of annular plastic seats that were compacted between the ball member and the wall portions of end fittings. Such seat designs suffered from a number of problems including low sealing forces at low pressure or vacuum conditions, and valve leakage due to wear and tolerance errors.
These early seat designs gave way to a contoured seat design in which the ball member was engaged along its outer periphery by a narrow band or line contact. Wear problems also developed with contoured seat designs and they gave way to the development of the flexible seat. The flexible seat, though, only provided improved operation for short periods of time. A seat ring with a disc spring, as well as an upstream seat bypass arrangement, were other improvements developed by the industry which progressively overcame various problems associated with ball valve seating arrangements. The U.S. Pat. No. 4,410,165 describes a seal assembly which includes a support ring, a disc spring, and a seat ring. This assembly provides additional seat ring support in a floating ball type of valve which is applicable to use in high fluid pressure environments. A longer life span was, in turn, realized at a cost savings with respect to other known seating arrangements.
More specifically, the seat assembly structure of the U.S. Pat. No. 4,410,165 utilizes a pair of resilient seat rings disposed on opposite sides of the ball member. A disc spring is interposed between the end fittings and the seat rings to continuously urge the seat rings into sealing engagement with the ball member. A reinforcing or support ring is disposed at a forward surface of each seat ring for positive locating engagement with a shoulder extending into the valve chamber.
Commonly assigned patent application Ser. No. 542,399, now issued as U.S. Pat. No. 4,602,762, describes a similar seat ring assembly. It recognizes that a reinforcing or support ring need not necessarily be incorporated into the valve seal structure. Instead, any bearing surface disposed in the valve passageway for abutting engagement with the seat ring may be used with equal success.
These latter two arrangements have proved to be quite satisfactory, but after continued use in environments filled with contaminants, the open spaces or voids defined between the ball member, seal assemblies, and the valve chamber walls are subject to eventual contaminant deposit. This contaminant deposit has an adverse effect on the sealing integrity of the ball valve. It has, therefore, been deemed desirable to fill these open spaces or voids in ball valves to further limit the area available in the interior of the valve which could otherwise accommodate fluid flow around the ball. Any such arrangement should not interfere with or reduce the effectiveness of the seal assemblies themselves. The subject invention is deemed to meet these and other needs in providing a new low dead space ring construction.